Kyrgios fined $40k for Shanghai walk-off

Nick Kyrgios has been fined almost $A40,000 by the ATP on Wednesday after walking off the court during his opening match at the Shanghai Masters a day earlier.

The 13th-seed packed his bag and left the court after losing the first set 7-6 (7-5) to Steve Johnson on Tuesday.

He was booed from the court by the crowd.

Kyrgios was fined his first-round prize money of $A27,071, for failing to see the doctor following his retirement. According to ATP Tour rules, it is mandatory to be examined by a physician if injured. He was fined an additional $A12,840 for unsportsmanlike conduct.

Hours after he abandoned the match, Kyrgios offered an apology on Twitter and said he had a stomach ache and sore shoulder.

"I've been battling a stomach bug for the past 24 hours and I tried to be ready but I was really struggling on the court today which I think was pretty evident from the first point," Kyrgios said.

"My shoulder started to hurt in the practice which didn't help either and once I lost the first set I was just not strong enough to continue. I've not eaten much in the past 24 hours."

This was despite television footage and audio capturing him telling his courtside box he'd quit if he lost the first set in an apparent protest over the decisions of chair umpire Fergus Murphy.